Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$75.46	8.737%	$82.0529	$82.05	$82.05	$82.10
Purchase #2	$46.95	6.190%	$49.8562	$49.86	$49.85	$49.90
Purchase #3	$40.39	4.220%	$42.0945	$42.09	$42.10	$42.10
Purchase #4	$124.74	13.530%	$141.6173	$141.62	$141.60	$141.60
Purchase #5	$126.50	12.628%	$142.4744	$142.47	$142.45	$142.50
Purchase #6	$101.49	7.629%	$109.2327	$109.23	$109.25	$109.20
Purchase #7	$214.36	8.434%	$232.4391	$232.44	$232.45	$232.40
7 purchase totals =	$729.89		$799.7671	$799.76	$799.75	$799.80